NAME

       curl_easy_header - get an HTTP header

SYNOPSIS

       #include <curl/curl.h>

       CURLHcode curl_easy_header(CURL *easy,
                                  const char *name,
                                  size_t index,
                                  unsigned int origin,
                                  int request,
                                  struct curl_header **hout);

DESCRIPTION

       curl_easy_header(3)  returns  a pointer to a "curl_header" struct in hout with data for the HTTP response
       header name. The case insensitive null-terminated header name should be specified without colon.

       index 0 means asking for the first instance of the header. If the returned header struct has  amount  set
       larger  than  1, it means there are more instances of the same header name available to get. Asking for a
       too big index makes CURLHE_BADINDEX get returned.

       The origin argument is for specifying which headers to receive, as a single HTTP transfer  might  provide
       headers from several different places and they may then have different importance to the user and headers
       using  the  same  name  might  be used. The origin is a bitmask for what header sources you want. See the
       descriptions below.

       The request argument tells libcurl from which request you want headers  from.  A  single  transfer  might
       consist  of  a  series  of  HTTP  requests and this argument lets you specify which particular individual
       request you want the headers from. 0 being the first request and then the number  increases  for  further
       redirects  or  when multi-state authentication is used. Passing in -1 is a shortcut to "the last" request
       in the series, independently of the actual amount of requests used.

       libcurl stores and provides the actually used "correct" headers. If for example two headers with the same
       name arrive and the latter overrides the former, then only the latter is provided. If  the  first  header
       survives  the second, then only the first one is provided. An application using this API does not have to
       bother about multiple headers used wrongly.

       The memory for the  returned  struct  is  associated  with  the  easy  handle  and  subsequent  calls  to
       curl_easy_header(3) clobbers the struct used in the previous calls for the same easy handle. Applications
       need  to  copy  the  data  if  it wants to keep it around. The memory used for the struct gets freed with
       calling curl_easy_cleanup(3) of the easy handle.

       The first line in an HTTP response is called the status line. It is  not  considered  a  header  by  this
       function. Headers are the "name: value" lines following the status.

       This function can be used before (all) headers have been received and is fine to call from within libcurl
       callbacks. It returns the state of the headers at the time it is called.

The header struct

       struct curl_header {
          char *name;
          char *value;
          size_t amount;
          size_t index;
          unsigned int origin;
          void *anchor;
       };

       The data name field points to, is the same as the requested name, but might have a different case.

       The data value field points to, comes exactly as delivered over the network but with leading and trailing
       whitespace  and  newlines  stripped  off.  The `value` data is null-terminated. For legacy HTTP/1 "folded
       headers", this API provides the full single value in an unfolded manner with a single whitespace  between
       the lines.

       amount is how many headers using this name that exist, within the origin and request scope asked for.

       index  is  the zero based entry number of this particular header, which in case this header was used more
       than once in the requested scope can be larger than 0 but is always less than amount.

       The origin field in the "curl_header" struct has one of the origin bits set, indicating  where  from  the
       header  originates.  At  the time of this writing, there are 5 bits with defined use. The undocumented 27
       remaining bits are reserved for future use and must not be assumed to have any particular value.

       anchor is a private handle used by libcurl internals. Do not modify.

ORIGINS

       CURLH_HEADER
              The header arrived as a header from the server.

       CURLH_TRAILER
              The header arrived as a trailer. A header that arrives after the body.

       CURLH_CONNECT
              The header arrived in a CONNECT response. A CONNECT request is being  done  to  setup  a  transfer
              "through" an HTTP(S) proxy.

       CURLH_1XX
              The  header  arrived  in  an  HTTP 1xx response. A 1xx response is an "intermediate" response that
              might happen before the "real" response.

       CURLH_PSEUDO
              The header is an HTTP/2 or HTTP/3 pseudo header

EXAMPLE

       int main(void)
       {
         struct curl_header *type;
         CURL *curl = curl_easy_init();
         if(curl) {
           CURLHcode h;
           curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
           curl_easy_perform(curl);
           h = curl_easy_header(curl, "Content-Type", 0, CURLH_HEADER, -1, &type);
           curl_easy_cleanup(curl);
         }
       }

AVAILABILITY

       Added in 7.83.0. Officially supported since 7.84.0.

RETURN VALUE

       This function returns a CURLHcode indicating success or error.

SEE ALSO

       curl_easy_nextheader(3),   curl_easy_perform(3),   CURLINFO_CONTENT_TYPE(3),   CURLOPT_HEADERFUNCTION(3),
       libcurl-errors(3)

libcurl 8.5.0                                   December 04, 2023                            curl_easy_header(3)